The Joso High Bridge

This viaduct in southeast Washington state hits an interesting level of obscurity: there’s an article on it the German version of Wikipedia, but not the English version. Fortunately, there’s a HAER survey to provide some photos for today’s High Bridge.

This is another steel viaduct with a lot of spans. Really a lot: 55 spans (including the short spans over the towers) for a total length of about 3900 feet (1.2 km). It was constructed over the Snake River in 1910-1914 by the Union Pacific Railroad, which still runs trains on it. The height…that’s another gray area. It was constructed at 261 feet above the river, but this part of the river was turned into a lake by the Lower Monumental Dam. The dam is 100 feet high, but didn’t raise the water level at the bridge by that much: the bridge deck is now roughly 190 feet above water. The HAER photos were taken in 1993, so they show the bridge in its post-dam, less-high state. The photos show piers where the towers meet the river, suggesting that the bases of the old towers were encased in concrete.

It’s still an impressive structure in a rather empty setting:

The construction photos show each span being cantilevered from the last, which is feasible with the main (river) spans being only 248 feet long. The approaches and the short spans over the towers are simply built-up plate girders, the main spans are warren deck trusses. Even before the river was raised, this is an overwhelmingly long bridge: despite its height it feels low because it is so long. There are portions of the Snake River in a deep and narrow gorge, but this wasn’t one even before the dam.

In short: this is a low high bridge.

1 thought on “The Joso High Bridge”

  1. Pingback: The Joso High Bridge — Old Structures Engineering – The Bridgehunter's Chronicles

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